Though I see now after I enroll in a contest that Brazil is not in the list of eligible countries, believe that there is no problems. I live in Brazil and have won tender in England (London) and received awards normally. The awards were sent to me without charges or taxes, because it is a cultural competition and seeks growth in the use of awarded prizes.

The laws regarding contests are different in different countries (for instance, in some countries, the contests here count as gambling, and you are only allowed to run a contest in Quebec if you are based in Quebec), and it takes a lot of lawyer-time to make sure the terms and conditions of the contests make the contests legal in each country.

If you read the rules of the contests, the number of eligible countries is usually limited to entries from US, Canada [excluding Quebec], UK, China, Belgium, the Netherlands, Australia, Colombia, Germany, Switzerland, Norway, India, and Denmark.

For most contests, being 17 is fine - you will just need to get parental permission to receive a prize, should you win.

If you are not in an eligible country, you can get around that by finding a collaborator* who does live in an eligible country. If you win, the collaborator can give their details to HQ for prize delivery, and then pass your share on to you.

*To prevent possible arguments over who gets what, collaborators should be people you actually know, maybe even family or a friend. To enable collaboration on a project, go to the Edit page, and select "Collaborate" from the "More" drop-down menu. You will then be able to add user-names to the list of collaborators. Collaborators can edit text and add photos, but only the main author can hit the "publish" button.